LTC3456_15 Datasheet, PDF (1/28 Pages) Linear Technology – 2-Cell, Multi-Output DC/DC Converter with USB Power Manager

LTC3456
2-Cell, Multi-Output
DC/DC Converter with
USB Power Manager
FEATURES
■ _{Seamless Transition Between 2-Cell Battery, USB}
and AC Wall Adapter Input Power Sources
■ _{Main Output: Fixed 3.3V Output}
■ _{Core Output: Adjustable from 0.8V to VBATT(MIN)}
■ _{Hot Swap}^TM _{Output for Memory Cards}
■ _{All Outputs Discharged to Ground During Shutdown}
■ _{Power Supply Sequencing: Main and Hot Swap}
Outputs Come Up After Core Output
■ _{Accurate USB Current Limiting}
■ _{High Frequency Operation: 1MHz}
■ _{High Efficiency: Up to 92%}
■ _{Small (4mm × 4mm × 0.75mm) 24-Pin QFN Package}
U
APPLICATIO S
■ _{GPS Portable Navigators}
■ _{MP3 Players}
■ _{Digital Cameras}
■ _{Handheld Computers}
DESCRIPTIO
The LTC^®3456 is a complete power management system
IC optimized for a variety of portable applications. The
device generates two separate power rails: a 3.3V (fixed)
Main supply and a 1.8V (adjustable) Core supply. In
addition, the LTC3456 contains a USB power manager, a
Hot Swap output, a low-battery indicator and an always-
alive V_MAX output. The LTC3456 takes power from one of
three sources: a Wall adapter, a USB port or a 2-cell
Alkaline/NiCd/NiMH battery, in that order of priority. Cur-
rent drawn from the USB port is accurately limited to
100mA or 500mA based on the state of the USBHP pin.
The Main and Core switchers are all high efficiency, 1MHz
fixed frequency PWM converters. Availability in a small
(4mm × 4mm × 0.75mm) 24-pin QFN package makes the
LTC3456 ideal for space-sensitive portable devices.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including 5481178,
6580258, 6304066.
TYPICAL APPLICATIO
2 AA ⁺
CELLS
4.7µF
L2
4.7µH
L3
10µH
V_INT
3.3V
22µF
USB POWER
(4.35V TO 5.5V)
AC WALL
ADAPTER
(5V ±10%)
4.7µF
1Ω
4.7µF
1Ω
100k
V_BATT
AIN
80.6k
AO
SW2_BST
SW2_BK
USB
CONTROLLER
USBHP
SUSPEND
V_INT
V_MAIN
HSO
USB
LTC3456
SW1
1k
EXT_PWR
V_EXT
FB1
11.3k
10µF
4.32k
ON/OFF
WALLFB
PWRKEY
V_MAX
PBSTAT RESET MODE PWRON PGND AGND
L1
10µH
100k
MAIN OUTPUT
3.3V
1µF ^150mA
Hot Swap OUTPUT
3.3V
1µF ^50mA
CORE OUTPUT
1.8V
10µF ^200mA
220pF
80.6k
V_MAX
(POWERS
1µF ^{REAL-TIME CLOCK)}
µP
3456 TA01
Efficiency and Power Loss
vs Load Current
(Battery Powered)
100
250
V_BATT = 2.4V
90 MODE = 0V
80
200
70
1.8V
OUTPUT
3.3V
OUTPUT
60
150
EFFICIENCY
50
40
POWER LOSS
3.3V
OUTPUT
100
30
20
50
1.8V
10
OUTPUT
0
0
1
10
100
1000
LOAD CURRENT (mA)
3456 TA01b
3456fa
1